how do you mess with songs like remix them and delay them?

Answer 1

Try a program called adobe audition, used to be called cool edit pro. Has multi tracking, mixing, all kinds of features to use.

Answer 2

Well, back in the '80's we played around with a 4-track tape recorder (where you could input 4 separate tracks, either simulateously or at different times). You could also play a track through a sound effects device for reverb, echo, etc., and record it back into the 4-track.

These days it's probably even better fun.